1. Field of the Invention
The present invention relates to a side airbag device which includes an airbag adapted to be mounted on a backrest of a seat of a vehicle in a folded-up configuration and a limitation member which is disposed around the airbag for constraining airbag deployment.
2. Description of Related Art
JP 2001-354103A discloses a known side airbag device which includes a limitation member disposed around a folded-up airbag. The limitation member includes a tearable seam.
In this conventional side airbag device, when, at airbag deployment, an obstacle such as a vehicle occupant is situated in front of the front side of a housing area in which the folded-up airbag is stored, the limitation member constrains the airbag from protruding forward. When the occupant is seated in his normal seating position (i.e., in a normal protecting situation), the tearable seam of the limitation member is torn due to increase of the internal pressure of the airbag, and the airbag is deployed at a side of the occupant.
According to the description of the paragraph 0039 of the prior art reference specified above, however, the airbag stays checked from unfolding by the limitation member and only a comparatively low pressure is built up in the airbag when the obstacle such as an occupant is located in proximity to the deploying airbag. This description implies that the limitation member itself is inflatable with an inflation gas when the obstacle is located in proximity to the deploying airbag. It is also presumed that the limitation member has a bag-like contour and covers the airbag all over. In a normal protecting situation, the airbag of this conventional side airbag device tears a tearable seam of the limitation member and completes deployment when having gained an enough pressure. However, if the limitation member has a bag-like contour as presumed above, it is presumed that the airbag will not be inflated quickly because the tear seam should not be torn quickly.